To demonstrate that data from the Stroke and Traumatic Coma Data Banks are reliable, studies of inter-observer agreement have been conducted. These studies included examination of variation in neurological examination, diagnosis and CT scan reading. A paper on observer agreement in stroke diagnosis is in press. The paper reports that high levels of agreement in diagnosis of stroke mechanism have been reached among neurologists collaborating in a common research effort. Diagnosis of stroke type was generally more reliable than individual signs and symptoms. A manuscript on observer agreement in CT readings of stroke anatomy has been submitted for publication. In general, levels of agreement were excellent for detection of infarcts and ICH. Substantial agreement was also obtained on whether or not the CT was normal and on indications of small and deep infarcts, superficial and deep infarcts, and aneurysms.